Ня (nya) is an expression of a tender emotion, one that people have towards
cats or very cute people like Natalia Poklonskaya. Nya originates from japanese and means "meow", it was adopted in
Russian language from
anime.
Няша (nyasha) — a word for a person that you feel "nya" for. The today's use of the word is originating from the "nya" or at least is very close emotionally to "nya", although it used to mean a "bottom of a dried lake, the one with dirt and bad smells"
Nyash-myash is a part of the Natalia's speech where she was asked about her online fame. The "myash" here is a word play that Jewish,
Russian, Ukrainian and some other people use to playfully and non-angrily diminish the importance, like "
bagel-schmagel", "president-schmesident" or "sashlik-mashlik".